Molar absorptivity and A 1 cm 1% values for proteins at selected wavelengths of the ultraviolet and visible regions. XXII

The molar absorptivity and A _{1 cm} ^1% values for 150 proteins are reported. The conditions under which these values were obtained and citations to the sources of the data are also provided.     

Molar absorptivity and A 1cm 1% values for proteins at selected wavelengths of the visible and ultraviolet regions. XXIV

The molar absorptivity and A _1cm ^1% values for 154 proteins are reported. The conditions under which these values were obtained and citations to the sources of the data are also provided.     

核磁共振研究二茂铁硒铂配合物构象交换热焓

The intramolecular conformational exchange thermodynamics of cis-PtCl[1,1'bis(undecenylseleno)ferrocene](B11SeFcPt) in CDCl3 solution was studied by one dimensional proton NMR． The chemical equilibrium constants were obtained directly from the integration of the 1H NMR spectra and the enthalpy as a function of temperature for the conformational exchange of B11SeFcPt was calculated from the equilibrium constant.     

Resonant Ionic,Covalent Bond,and Steric Characteristics Present in 1Σu+ States of Li2

The molecular bonding in the excited states of the alkali dimers involves the resonant ionic, covalent bond and steric interactions. We show here the case of the ¹Σ_u⁺ states of Li₂ by ab initio calculation. These interactions as functions of the internuclear distance lead to complex potential energy curves, providing an important application for high resolution laser spectroscopy. The spectroscopic constants for the 4 and 5 ¹Σ_u⁺ states are obtained for the first time.     

CCl2(A 1B 1,a3B1)自由基被烷烃类分子猝灭动力学

用放电 LIF实验装置,对CCl4/Ar混合气体放电产生CCl2自由基,再用541.52 nm激光将电子基态CCl2激励到激发态A 1B1(0,4,0)振动能级上,通过检测激发态CCl2时间分辨荧光信号,测得室温下CCl2(A 1B1)被烷烃类分子猝灭的实验结果,用我们提出的三能级模型分析处理实验数据,获得CCl2(A 1B1)态和CCl2(a 3B1)态的碰撞猝灭速率常数kA和ka值.     

1H, 13C,and 14N NMR study of 3-methylfurazans with nitrogen-containing substituents at position 4

3-Methylfurazans with nitrogen-containing substituents at position 4 were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. A correlation between the chemical shifts in ¹³C NMR spectra of these furazans and monosubstituted benzenes with the same substituents was found. The increments for a number of furazan-containing substituents were determined for the first time.     

The statistical generation of SCS values and interaction factors for the13C NMR spectra of arenes

A new methodology which statistically determines substituent chemical shifts (SCS) and interaction factors of adjacent groups for use in the³C NMR spectroscopy of arenes is described. From a data base of 15,255 signals we have computed several hundred of thesestatistical SCS values (SSCS values), and interaction factors for many common pairs of groups. Some interaction factors for 1,2,3-substitution are also reported. When these SSCS values and interaction factors are used to predict the signal position they are found to give a correlation coefficient of predicted verses observed values of 0.994 with a standard deviation of 1.5 ppm.     

Accurate values for the nonrelativistic energies of the lowest singlet and triplet S-states of the4He-Isotop

Accurate lower and upper bounds for the nonrelativistic lowest energies¹ E ₀ and³ E ₀ of the singlet and triplet-system of the⁴He-Isotop are calculated with the linearized method of variance minimization. The same was done for¹ E ₁ the energy of the first excitedS-state 2¹ S. The results especially for¹ E ₀ and³ E ₀ in a.u. are −2.9033076997₅ ≤¹ E ₀ ≤ −2.9033076921₈ −2.1749324263₇ ≤³ E ₀ ≤ −2.1749324245₉ i.e. the values are determined with an absolute error smaller than 0.00167 cm⁻¹ for¹ E ₀ and 0.00039 cm⁻¹ for³ E ₀.     

1H-n.m.r. studies on the complex formation ofN,N-dimethylbiuret with alkali and alkaline earth salts

¹H-n.m.r. spectra ofN,N-dimethylbiuret inDMSO containing LiI, LiCl, NaI, KI, RbI, CsI, MgCl₂, CaCl₂, SrCl₂, BaCl₂ and BaI₂ have been investigated. The observed shifts of the NH-signal are relatively stronger than the shifts of the NH₂-signals. At high salt concentration, coalescence of the NH₂-signals and anion effects are observed.

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¹H-NMR Untersuchungen zur Komplexbildung vonN,N-Dimethylbiuret mit Alkali- und Erdalkalisalzen

Zusammenfassung Protonenkernresonanzspektren vonN,N-Dimethylbiuret inDMSO-Lösungen mit LiI, LiCl, NaI, KI, RbI, CsI, MgCl₂, CaCl₂, SrCl₂, BaCl₂ und BaI₂ wurden aufgenommen. Die beobachteten Verschiebungen des NH-Signals sind stärker als die der NH₂-Signale. Bei höheren Salzkonzentrationen wird Koaleszenz der NH₂-Signale und das Auftreten von Anioneffekten beobachtet.

     

Simultaneous enzyme immunoassay for the screening of aflatoxin B1 and ochratoxin A in chili samples

Membrane-based immunoassay has been developed for simultaneous estimation of aflatoxin B₁ (AFB₁) and ochratoxin A (OA) in chili samples. The combined estimation of both the mycotoxins is more economical in respect of time, work and materials than two separate assays. The method uses a low cost test device consisting of a membrane with immobilized anti-AFB₁ and anti-OA antibodies and a filter paper attached to a polyethylene card below the membrane. It allows direct analysis of sample extracts containing substantial amount (40%) of methanol. This permits the use of two-fold diluted sample extracts resulting in minimum dilution error. The limit of quantitation obtained was 2 and 10 μg kg⁻¹ for AFB₁ and OA, respectively. The tolerance of 40% methanol was found to be due to the application of small size (0.8 mm diameter) spots on membranes, as the tolerance decreases to 20% with gradual increase in spot size. The combined method is capable of producing acceptable results to analyze AFB₁ and OA in chili with accuracy and precision. The AFB₁ and OA values obtained for spiked and naturally contaminated chili samples by the simultaneous method were in good correlation with those measured by individual ELISA. The method offers a simple, rapid and cost-effective screening tool to meet the requirements of the rapidly evolving EU legislation.     

Thermodynamic investigations on derivatives of pyrimidine nucleic acid bases: Joint use of calorimetric, volumetric and structural data for the description of properties of pyrimidine nucleic acid bases and their derivatives

The experimental enthalpies of solution Δ_solH_m^∞, van’t Hoff enthalpies of sublimation Δ_s^gH_m⁰ of solid compounds, partial molar volumes V₂⁰, and partial molar heat capacities C_p,2⁰ of aqueous solutions of pyrimidine nucleic acid bases and their derivatives, determined previously and collected here, are discussed in terms of calculated structural parameters. Relations have been established between the calorimetric and volumetric properties. Correlations have been developed to relate both the enthalpies of solvation and the partial molar heat capacities to the polar and apolar parts of the accessible molecular surface areas.     

Determination of pKa values of tenoxicam from H NMR chemical shifts and of oxicams from electrophoretic mobilities (CZE) with the aid of programs SQUAD and HYPNMR

In this work it is explained, by the first time, the application of programs SQUAD and HYPNMR to refine equilibrium constant values through the fit of electrophoretic mobilities determined by capillary zone electrophoresis experiments, due to the mathematical isomorphism of UV-vis absorptivity coefficients, NMR chemical shifts and electrophoretic mobilities as a function of pH. Then, the pK_a values of tenoxicam in H₂O/DMSO 1:4 (v/v) have been obtained from ¹H NMR chemical shifts, as well as of oxicams in aqueous solution from electrophoretic mobilities determined by CZE, at 25 °C. These values are in very good agreement with those reported by spectrophotometric and potentiometric measurements.     

Spin-spin coupling constant 3 J H,F as a reliable criterion for recognition of individual regioisomeric and tautomeric pairs of H(CF2)2-containing isoxazoles and pyrazoles

The spin-spin coupling constant ³ J _H,F of the H(CF₂)₂ group varies within 1.6—3.5 Hz for 5-R^F- and 3.8—4.5 Hz for 3-R^F-isoxazoles and pyrazoles in CDCl₃ and can serve as a reliable criterion for recognition of regioisomeric and tautomeric structures of H(CF₂)₂-containing heterocyclic compounds.     

氨蒸发诱导法制备纳米结构LiNi1/3Co1/3Mn1/3O2及其作为高功率型锂离子电池正极材料的性能

采用氨蒸发诱导法成功制备出纳米结构LiNi_1/3Co_1/3Mn_1/3O₂正极材料,借助X射线衍射（XRD）分析、扫描电镜（SEM）、透射电镜（TEM）、高分辨率透射电镜（HRTEM）、能量分散谱（EDS）和比表面测试等表征手段及恒电流充放电测试研究了其晶体结构、微观形貌和电化学性能. 研究表明该方法制备出的材料具有良好的α-NaFeO₂层状结构,阳离子混排程度低. 纳米片交错堆积而成核桃仁状形貌,片与片之间形成许多纳米孔,而且纳米片的侧面属于{010}活性面,能够提供较多的锂离子的脱嵌通道. 在室温下及3.0-4.6 V充放电范围内,该材料在电流密度为0.5C、1C、3C、5C和10C时放电比容量分别为172.90、153.95、147.09、142.16 和131.23mAh·g^-1. 说明其具有优异的电化学性能,非常有潜力用于动力汽车等高功率密度锂离子电池中.     

Generalized quantum mechanical two-centre problems. IV. On the accuracy of simple LCAO approximations for H 2 + states and the Eckart criterion

If x denotes an exact solution of the quantum mechanical two centre Coulomb problem, we optimize a normalized LCAO approximation by making the overlap S = (x¦) a maximum. In this context we study how a weight factor (r _a r _b )^–1 in the definition of the inner product changes the approximation and the expectation value of electronic energy. Finally we compare the lower bound given by the Eckart criterion with the exact overlap. Results are reported for H ₂ ⁺ states 1s_g and 2p_u.Dedicated to Professor Hermann Hartmann on occasion of his 70th birthday on May 4th, 1984     

Relative stability of the2 A 1g and2 E g states of the C2H 6 + ion

Anab initio study of the relative stability for the states² A _1g and² E _g of C₂H ₆ ⁺ has been carried out. The results of the Open Shell Restricted Hartree-Fock calculations lead to assign the² A _{1 g} as the ground state of the molecule in agreement with previous SCF calculations.The correlation energy associated to both states has been calculated within the correlation hole model and the results, contrary to those obtained from Configuration Interaction calculations, do not alter qualitatively the conclusions from SCF.     

PVT properties of concentrated aqueous electrolytes. III. Volume changes for mixing the major sea salts at I=1.0 and 3.0 at 25°C

The densities of mixtures of the six possible combinatons of the major sea salts (NaCl, Na₂SO₄, MgSO₄, and MgCl₂) were determined at constant ionic strengths of I=1.0 and I=3.0 at 25°C. The results are used to determine the volume changes for mixing (V _m ) the major sea salts. The values of V _m were fit to equations of the form V _m where y _i is the molal ionic strength fraction of solute i, and ₀ and ₁ are parameters related to the interaction of like-charged ions. The cross-square rule was found to hold at both ionic strengths. Density estimates were made without and with the addition of volume of mixing terms to Young's Rule and compared to the experimental values. The densities calculated with the addition of volume of mixing terms gave better estimates, demonstrating that the densities of concentrated brines can be more accurately estimated using V _m terms. The equations of Reilly and Wood which include the cross-square rule were used to estimate the densities of the cross mixtures (NaCl–MgSO₄ and MgCl₂–Na₂SO₄). The estimated densities agree with the measured values to within ±30 ppm at I=1.0 and ±125 ppm at I=3.0.     

Capillary electrophoresis procedure for the simultaneous analysis and stoichiometry determination of a drug and its counter-ion by using dual-opposite end injection and contactless conductivity detection: Application to labetalol hydrochloride

In this work, a capillary electrophoresis (CE) procedure was developed for the simultaneous determination of a pharmaceutical drug and its counter-ion, namely labetalol hydrochloride. For this purpose, an uncoated fused-silica capillary, a low conductivity background electrolyte (BGE) and a capacitively coupled contactless conductivity detector (C⁴D) were employed. This detection system is highly sensitive and enables detection of inorganic as well as organic ions unlike with direct UV detection. Moreover, to be able to simultaneously analyze the cationic drug (labetalol⁺) and its anionic counter-ion (Cl⁻) in the same electrophoretic run without the need of a coated capillary, a dual-opposite end injection was performed. In this technique, the sample is hydrodynamically injected into both ends of the capillary. This method is simple and easy to perform since the different injection steps are automated by the CE software.This novel CE-C⁴D procedure with dual-opposite end injection has been successfully validated and applied for the analysis of chloride content in an adrenergic antagonist (labetalol hydrochloride). Thus, the hereby developed method has been shown to enable fast (analysis time < 10 min), precise (repeatability of migration times < 0.7% and of corrected-peak areas < 3.3%; n = 6) and rugged analyses for the simultaneous determination of a pharmaceutical drug and its counter-ion.